During material processing by lasers it is desirable to be able to view the part or material to be processed along the axis of the laser beam, that is, to look at the part the same way the laser does. Such devices make part alignment much easier and much more accurate. As a result, product quality may increase along with improvement in process yield.
Devices are known for through-the-lens observation of the workpiece, which usually consist of a mirror or a prism that is moved in and out of the path of the laser beam. The primary disadvantage of such devices resides in that they must be removed from the beam path before the laser may be operated.
Other devices are known for similar observations which, however, require specially constructed mirrors, such as ring mirrors, to allow the power beam to pass through the middle of the optic.